1. Technical Field
The present invention generally relates to an active device array substrate and a testing method thereof and, particularly to, an active device array substrate which can prevent circuits thereof from being damaged by electrostatic charges through testing pads and a testing method of the active device array substrate.
2. Description of the Related Art
Since active flat display panels have the advantages of small size, light weight and fast response, the active flat display panels are widely applied on various electronic products. An active flat display panel generally is consisted of an active device array substrate, a display layer and a light-transmissive substrate. The display layer is sandwiched between the active device array substrate and the light-transmissive substrate and can be, for example a liquid crystal layer of a liquid crystal display (LCD) panel or an electrophoretic layer of an electrophoretic display (EPD) panel and so on.
FIG. 1 is a schematic view of a conventional active device array substrate. Referring to FIG. 1, the active device array substrate 100 has a display area 102 and a peripheral circuit area 104. The display area 102 has a plurality of pixel units 110 formed therein. The peripheral circuit area 104 has a plurality signal lines 120 formed therein for electrically connecting the pixel units 110 in the display area 102 to driver circuits 130.
A manufacturing process of a conventional active flat display panel is taken as an example, after completing the arrangement of all circuits on the active device array substrate 100, a circuit testing subsequently is performed to check whether the circuits on the active device array substrate 100 have defects or not. Therefore, testing pads 140 would be arranged in the peripheral circuit area 104 of the active device array substrate 100, and a testing tool (e.g., a probe, not shown in FIG. 1) can be connected with the circuits on the active device array substrate 100 through the testing pads 140.
However, regardless of a manufacturing apparatus, an operator or the active device array substrate 100, they would accumulate lots of electrostatic charges thereon. Therefore, when the active device array substrate 100 is in contact with the manufacturing apparatus, the operator or other objects in the manufacturing process, the electrostatic charges are prone to transfer to the active device array substrate 100 by the charged bodies and then are delivered to the circuits in the display area 102 through the signal lines 120 from the testing pads 140. As a result, the circuits in the display area 102 would suffer from electrostatic damage so that the active device array substrate 100 is destroyed.
FIG. 2 is a sectional view of the active device array substrate of FIG. 1, taken along lines I-I′. Referring to FIGS. 1 and 2, in order to avoid the electrostatic charges on the active device array substrate 100 to arrive in the display area 102 from the testing pads 140, a proposed design in the prior art is to firstly form a dielectric layer 125 on the signal lines 120 and then form the testing pads 140 on the dielectric layer 125 which is disposed above the signal lines 120. In other words, the testing pads 140 and the signal lines 120 have the dielectric layer 125 included therebetween, so as to avoid the electrostatic charges to be directly transferred to the circuits in the display area 102 through the signal lines 120 from the testing pads 140. Each of the testing pads 140 have a dielectric layer 150 and a conductive layer 160 formed thereon in sequence. The dielectric layer 150 has an opening 152 and the conductive layer 160 is electrically connected with the testing pad 140 through the opening 152. When performing a testing, a laser beam can be used to weld the testing pad 140 and the signal line 120 and the testing tool is electrically connected to the conductive layer 160, the circuits on the active device array substrate 100 then can be tested.
However, before using the laser beam to weld the testing pad 140 and the signal line 120, since the testing pad 140, the dielectric layer 125 and the signal line 120 cooperatively constitute a capacitor C, although the electrostatic charges would not be directly transferred to the signal line 120 from the testing pad 140, when the testing pad 140 has excessive electrostatic charges accumulated thereon, a phenomenon of electrostatic breakdown would be occurred in an instant, which would cause serious damage applied to the active device array substrate 100.